各位写一下，实在一点不会

百度上都有答案，先百度。

2.
void main()
{
int num,n1,n2,n3;
scanf("%d",&num);
n1=num/100;
n2=(num-n1100)/10;
n3=num%10;
printf("%d:%d,%d,%d",num,n1,n2,n3);
return 0.
}
3.
void main()
{
int num;
scanf("%d",&num);
printf("%ld,%ld",numnum,numnumnum);
return 0;
}
4
void main()
{
int x,y,max;
printf("please enter two numbers:");
scanf("%d,%d",&x,&y);
if(x>y）max=x;
else max=y;
printf("%d\n",max);
return 0;
}

5.void main()
{
char c;
scanf("%c",&c);
if(c>="a" and c<="z") c=c-32;
if(c>="A" and c<="Z") c=c+32;
printf("%c\n",c);
}

7
void main()
{
int num,n1,n2,n3;
scanf("%d",&num);
n1=num/100;
n2=(num-n1100)/10;
n3=num%10;
if(num==n1n1n1+n2n2n2+n3n3n3)
printf("yes\n");
else
printf("no\n");

}